HV, is high volume, most shocks (especially) fox now tend to be high volume nowdays, to the point where you get ‘rings’ to put inside the shocks to reduce the volume to self-tune it. HV vs LV is due to spring rate IIRC, but basically if your bike came with one, your probably best buying another the same.
I know there a bargains to be had on the internet/ebay, but getting your shock from a suspension specialist, they will/should give it the right tune for your bike before it is sent out… saving you money having the 2nd hand/cheap bargain tuned (& serviced.. which is why most shocks are on ebay) later.
Loco, TF-Tunes, or J-tech (& others) will all be able to help..